Sorry Ana but not the mail box... the mail tubes.... they are in a office. You had to find 3 tubes to put into the tube slots and then press buttons on top of the slots. Ya know like those tubes you use at the drive thru at banks. Thanks for any and all help. nawahtel

I am not sure where exactly you are in the game, but there is a series of YouTube videos that shows you a walkthrough for the game. It's in another language but you should still be able to see a solution to your puzzle there:

sorry nawahtel, I haven't played and the only thing I can find says their is a mailbox code 473. I have been unable to locate anything else related to mail. Hopefully someone that has played will be by to help you.